Delicate workpieces, which include in particular optical lenses and other optical structural elements, must be held as gently as possible for various purposes, in particular for transport into a processing machine or out of a processing machine.
Known are holding devices with a vacuum suction apparatus. Vacuum suction devices are only applicable if the surface of the workpiece permits one gasket edge of the suction apparatus to be applied in an air-tight manner against the workpiece. Only then is it possible to create an underpressure or vacuum. A secure hold of the workpiece is only assured if an open or continuous vacuum system is used, so that a small leak does not lead to a reduction of the vacuum. An open vacuum system, however, has the disadvantage that dirt can be sucked into the system. This danger is particularly great in processing machines such as lens grinding machines, where grinding dust accumulates and work must be done with a cooling medium. A conventional indirect vacuum system which is sealed off against dirt does not have a sufficiently secure holding action, since small leaks lead to a quick pressure increase and thus the suction force drops quickly. Furthermore, the direct sucking on of workpieces has the danger that, during suction, the workpiece surface is damaged.
Also known are holding devices with collets of plastic or metal. Workpieces can be held securely therewith, but the danger exists that the workpieces are impermissibly deformed and possibly destroyed by clamping forces which are too great and are applied to a relatively small area of the workpiece.
A basic purpose of the invention is to produce a holding device for delicate workpieces, in particular for optical lenses, with which the workpieces can be held just as securely as with the known collets, but where the holding is deformation-free and without any danger of destruction.